Polka Dot Icing Cake with Strawberry & Rhubarb

Today is Lisa's birthday! And it only seemed right to be celebrating with cake. Polka dot-covered cake to be exact. With some of our favourite flavours; strawberry, ginger and rhubarb. I may have thrown a bit of brown butter and vanilla bean into the mix too. I couldn't help myself. You might recognise the plate the cake is sitting on from the birthday cake she made me. It has taken me this long to return it to her, I am a terrible friend. But now I can officially dub us the sisterhood of the travelling cake plate. We had to laugh at the people who saw the photo of my cake on Facebook and were shocked that I was presenting her birthday cake with a giant slice cut out of it. If anyone was going to be okay with this, it would be Lisa. She did the same thing for my birthday after all. I guess it's something that only baking bloggers will understand.

The super adorable rainbow polka dot icing is made entirely of my regular butter icing, no sprinkles or fondant here! I got the idea from the amazing i am baker, I couldn't believe I hadn't thought of using dots of icing to decorate a cake before. Instead of just decorating the rim of the cake, I covered the entire thing with polka dots. As we are both lovers of all things print, I knew she would love it. There was a moment when I only had pink and green dots all over the cake that I was worried it was looking a bit like a pimple and mould covered cake but it got a lot cuter once I added a whole array of coloured spots. So fun! Yeah my whole kitchen was covered in rainbow smears of icing, but it was worth it.

The cake is a fresh strawberry cake that I've made several times in the past, it's lovely to eat as you get little pockets of baked strawberry pieces, mixed with the jam-like rhubarb and ginger icing that is sandwiched between the cake layers. I made my cakes in my super small but tall cake tins to achieve that great height on the cake but it will work just as well in a normal sized cake tin, albeit slightly shorter.

Polka Dot Icing Cake with Strawberry & Rhubarb

(adapted from this recipe, makes a tall 3-layer 15cm (6") cake or a shorter 3-layer 18cm (7") cake)

For the fresh strawberry cake:

170g (1.5 sticks) butter, softened

3 cups (about 420g) plain flour

3 tsp baking powder

1/2 tsp salt (if using unsalted butter, add an extra 1/2 tsp)

1 1/2 cups (300g) plus 2 tbsp sugar

2 eggs, room temperature

1 cup milk

1 tsp vanilla bean paste or pure vanilla extract

2 punnets (500g/1 pound) strawberries, hulled and halved

1. Grease and line three 15cm (6") or 18cm (7", will result in slightly thinner layers) round cake tins and preheat oven to 180°C (350°F). 
2. Sift flour, baking powder, and salt together into a medium bowl. 
3. Place butter and 1.5 cups sugar in a large mixing bowl and beat with an electic mixer on high speed until pale and fluffy, at least 5 minutes. 
4. Reduce speed to medium-low; mix in egg, milk, and vanilla.
   Reduce speed to low; gradually mix in flour mixture until just combined.
5. Split mixture between the three prepared tins and smooth tops with a spatula. Arrange strawberries on top of batter, cut sides down and as close together as possible. Sprinkle remaining 2 tablespoons sugar over berries. 
6. Bake cakes for 10 minutes. Reduce oven temperature to 160 degrees. Bake until cakes are golden brown and firm to the touch, and a skewer inserted into a non-strawberry part of the cake comes out clean, about 40-50 mins but timing will vary depending on your tin size (if on top and bottom rack, switch cakes between racks halfway through, baking). Let cool in tin on a wire rack, then turn out. Can be stored in an airtight container for a day or so before icing.

For the rhubarb filling:

1 bunch rhubarb (about 200g/7oz, trimmed weight), chopped into 2cm thick pieces

50g (1/4 cup) sugar (or more to taste)

Grated zest of 1/2 a lemon

Optional: 1/2 tsp finely grated ginger

200g butter, softened (Optional: I browned my butter using this method, but you can skip this to save time)

300g (about 2 cups) icing (confectioner's) sugar,sifted

1. Place rhubarb, sugar, lemon and ginger in a medium saucepan. 
2. Stir over medium heat until sugar dissolved. Reduce heat slightly and simmer until rhubarb is very soft and sugar syrup is slightly thickened, about 5-10 minutes. Set aside to cool to room temp.
3. Can be stored in an airtight container in the fridge for several days, until ready to be mixed into filling.
4. Place butter in a large mixing bowl and beat on high with an electric mixer until smooth. 
5. With the mixer on low, gradually add icing sugar until combined, then beat on high until pale and fluffy. 
6. Gently fold rhubarb mixture into the icing (this may cause the icing to curdle slightly, it is easier to avoid if the rhubarb is not too cold)
7. Place one layer of strawberry cake on your cake stand/plate. Spread a thick layer of rhubarb icing over the top and sandwich with another layer. Repeat. 
8. Crumb coat cake with remaining rhubarb icing. Chill in fridge until icing sets, at least 1 hour.

For the polka dot icing:

450g (4 sticks. Yes, really. You need extra to make all the coloured icings, especially if you want lots of colours.) butter, softened

700g (about 4.5 cups) icing (confectioner's) sugar, sifted

About 1/4 cup milk, adjust for the right texture

1 tsp pure vanilla extract

Variety of icing colourings, I used Wilton's gel icing colors

1. Place butter in a large mixing bowl and beat on high with an electric mixer until smooth. 
2. With the mixer on low, gradually add icing sugar, milk and vanilla until combined, then beat on high until pale and fluffy. You can add more milk or icing sugar to achieve the right texture of icing. You want it to be stiff enough to hold its shape but soft enough to pipe.
3. Use an offset spatula to cover your crumb coated cake in a layer of white icing. Regularly run your spatula under hot water to achieve a smoother finish.
4. Split the remaining icing into small bowls and add food colouring of your choice. Place each in separate piping bags with a narrow round tip, or use small ziplock bags with a tiny hole in one corner snipped off.
5. Carefully pipe colour dots all over the surface of your cake. Keep cake chilled until about 30 mins before serving, then remove from the fridge to allow it to come back to room temperature. Cake can be iced the night before serving.